1. Field of the Invention
The invention relates to a machine for producing and treating, or for treating a material web, and, more particularly, to a machine for producing and/or treating paper or paper board.
2. Description of the Related Art
Some papermaking machines permit the production and treatment, including application of an application medium to at least one side of the material web, in what is known as an online operation. In machines of this type, only contacting application apparatuses, such as coating units are conventionally used as the application apparatus.
Other machines may be used for the treatment, including the application of an application medium to at least one side of the material web, in what is known as an offline operation. Machines of this type include coating or application machines separate from a machine for producing the material web, to which the material web to be treated is generally fed in the form of material web reels. Within machines of this type, both contacting application apparatuses, such as coating units, and contactless application apparatuses, such as contactless coating units are used as application apparatuses.
Contacting application apparatuses can be a problem, inasmuch as the performance (runnability) and average operating times between operating interruptions can be impaired as a result of the contacting application or coating. Thus, there is an increased risk of a web break in the application unit resulting in the entire production line coming to a standstill.
As compared with an online operation, the offline operation has a lower volumetric efficiency in relation to the coating of the material web.
For many applications, a material quality with high smoothness and possibly gloss is desired. In order to achieve such a quality, the material web can be calendered online in a smoothing unit, possibly a two-roll soft calender, so as to be machine-finished or more highly machine-finished. Furthermore, there is a large number of material qualities which, conventionally, following the production of the material web in an appropriate machine, or following coating on a coating machine, have to be calendered offline in a further operation. Calendering exerts a substantial influence on the surface structure of the material, in particular of paper or board, and therefore both on the visual appearance and on the printability. Calendering is a very important operation for coated papers. Following coating, it provides smoothness and possibly gloss.
If the coating is carried out in an offline operation, the calendering is conventionally carried out in a separate offline process by way of a suitable smoothing machine, for example, a supercalender or soft calender, separate from the coating machine. On account of two offline processes being carried out, one after another, by way of separate machines, the result is an even lower volumetric efficiency.
What is needed in the art is a machine which has good performance and runnability and is able to provide material with a high smoothness and possibly gloss with a good volumetric efficiency.